me now to help explain the challenges of law enforcement is former secret service agent for barack obama, dan is with us. welcome back. one of the things i was thinking of today, and i know this is your area of expertise and having worked at the secret service and having protected barack obama, do you think as a matter of course being the boston marathon that they had bomb sniffing dogs prayer to the marathon? >> right, but we are assuming the bombs were placed there today when the security cordon was set up. but what if you got in before it was set up and pro placed an explosive. pennsylvania avenue doesn't have any devices but when he walked down we had the entire cordon set up. so don't assume they were put there today. >> what would be the process, then, as it relates to law enforcement when they have a big crowd like this? i assume you have to have bomb sniffing dogs going in and out at some point, right? >> right. but what we would do in the secret service and i don't know how practical for an event like the marathon, you have to clean the area out first. sweep it with the dogs, th